Method of treating synthetic yarns



March 19, 1963 A. F. G. MEERDINK 3,081,593

METHOD OF-TREATING SYNTHETIC YARNS Filed June 15, 1960 INVENTOR. ANTON FREDERIK GEORGE MEERDINK ahm A)! ATTORNEY United States Patent METHOD OF TREATING SYNTHETIC YARYS Anton Frederik George Meerdink, Velp, Netherlands,

assignor to American Enka Corporation, Enka, N.C.,

a corporation of Delaware Filed June 15, 1960, Ser. No. 36,330 Claims priority, application Netherlands June 25, 1959 2 Claims. (Cl. 57-157) This invention relates generally to a method for treating yarns formed from synthetic linear polycondensation products, especially po-lyamide yarns, and more particularly to an improvement in the processing of yarn which has been drawn, thereupon subjected to a treatment for internal relaxation, and subsequently wound or collected by means of a ring-twisting spindle.

It is generally known that certain yarn properties may be improved by drawing, hot relaxing and twisting the yarn. For carrying out this method, the apparatus is usually provided with a supply roller, a stretching or drawing roller, a de-tensioning device, a heating device positioned between said stretching roller and said detensioning device, and a-ring-twisting spindle. The supply roller and the stretching roller are so coupled, for example by a motor, that the circumferential speed of the stretching roller is a few times greater than that of the supply roller. The de-tensioning device may be formed by a pair of guiding rods over which the thread is passed with a light frictional engagement. As a result, the force exerted by the twisting spindle cannot run back up to the stretching roller and, therefore, the thread tension between stretching roller and guiding rods becomes so small that the thread may shrink. This shrinking may be accelerated by heating the thread between the stretching roller and the guiding rods. Shrinking of the thread may also be brought about without guiding rods if a light traveller is used.

The above-mentioned shrinking of the threads causes an internal relaxation or a removal of internal strain. The temperature at which the heating device is maintained depends on the threads to be treated. For threads consisting of polyamides based on adipic acid and hexamethylene diamine a heating may be considered at temperatures between 0 and 220 C. Threads consisting of polyamino caproic acid should be heated at 190 C. maximum whereas for threads from polyethylene terephthalate a maximum temperature of 220 C. is permissible.

The heating may take place with the aid of hot air or steam, by means of heated surfaces over which the threads to be relaxed are passed, or by applying heated inert liquids, such as hot mineral oil or molten metals through which the threads may be pulled.

A satisfactory heating may also be obtained with the aid of a freely rotatable metal thread guiding roller which is heated by an electrical element partly sur ounding the guiding roller at the points of thread contact. Internal relaxation also may be obtained by temporarily swelling the threads. Furthermore, said relaxation may be obtained by passing the threads to be treated through an air space over a greater than average distance before winding. This method, however, is less suitable for practical application since a greater distance is required between the stretching roller and the twisting spindle or the detensioning device, the latter being positioned in front of said spindle. See copending and commonly owned application Serial No. 708,689, filed January 13, 1958, now Patent No. 3,025,660.

Although the relaxation is preferably carired out in such a way that the threads are permitted to shrink, the latter is not absolutely necessary. A reduction of the internal strain may also be obtained by maintaining the thread 3,081,593 Patented Mar. 19, 1963 length constant during the relaxation. See copending and commonly owned application Serial No. 823,718, filed June 29, 1959.

The winding of the relaxed threads with the aid of a ring-twisting spindle preferably is carried out under a low tension, although the tension should be sufficiently high to prevent sagging of windings on the twisting pirn. In case the winding tension is too low, thread will not be easily separated from the thread conveying roller positioned immediately before the twisting spindle, which is undesirable. A minimum winding tension of 1 gram per tex. (1 tex.:9 denier), is generally required for preventing this difficulty.

The above-mentioned known methods are directed toward production of a yarn which does not produce the so-called barr effect when woven into fabric. The presence of or the blarr effect in a fabric means that streaks of varying conspicuousness occur at regular intervals in the fabric.

In connection with the foregoing, it is remarked that yarn wound on pirns by the known methods may be processed in many different ways. In the event that polyamide yarns are delivered in highly twisted form, the pirns which have been obtained on the draw twisting machines are rewound on so-called washing bobbins while using other twisting machines. On these bobbins the yarns are subjected to a treatment with hot water or steam in order to remove the twist liveliness contained therein, after which the yarn is rewound from said washing bobbins onto crosswound bobbins.

Fabrics which are manufactured with the use of said crosswound bobbins are totally free from the abovementioned b-arr effect. If, however, weaving yarns based on synthetic linear polycondensation products are required, especially polyamide yarns with a low twist, then the yarns on the draw-twist pirns are transferred to cops without intermediate twisting, and woven. With the latter method, however, the desired effect, namely an absence of barr in the resulting fabric, is not completely obtained. A certain barr effect remains perceptible and this must be ascribed to a tendency for barr to form in the processed yarns.

It is an object of this invention to provide a system for eliminating barr heretofore inherently resulting from Weaving into fabric yarn produced in the manner described above.

Surprisingly, it has been found that the aforesaid tendency for barr to form with low twist yarn which has been produced according to the above-mentioned method cannot be fully ascribed to the ineffectiveness of the applied relaxation treatment, but more importantly can also be attributed to certain circumstances before said yarns are processed into fabrics.

More specifically, it has been found that the time between Winding the stretched, relaxed and subsequently low twisted yarns on pirns and thereafter weaving of said yarns has a certain influence, in an adverse sense, on the tendency for barr forming. This means that, as has been surprisingly found, the tendency for forming draw-twist barr in the fabrics to be manufactured from the yarns increases when the time lapse between the processing operations mentioned is longer.

In the usual waiting period between processing stages, this tendency for barr forming is increased even to an extent that, although the quality of the freshly twisted yarns is satisfactory, the final results of the known method by which low twisted yarns are processed into fabrics must be considered to be unsatisfactory. By taking simple measures, however, this undesired increase of the tendency for barr forming of the low twisted yarns mentioned may be kept within an acceptable range.

The present invention consists in that in the above-mentioned known method the yarns are rewound from the pirns formed on the ring-twisting spindle onto crosswound bobbins before the tendency for forming a barr effect in said yarns has developed above a perceptible level. This means that the pirns formed on known draw-twisting machines and containing yarn which has been subjected to a treatment for internal relaxation, must be transferred into the form of a crosswound bobbin within a short time. Although this condition is generally satisfied by rewinding within one week, it is preferred that the rewinding be carried out within 48 hours.

In connection with this, it should be remarked that in the method for processing low twisted synthetic yarns into fabrics, which method has been followed hitherto and is considered to be known, the time elapsed between said winding in the form of twisting pirns :and weaving into fabric might take many weeks, and of course will vary from case to case, as when the weaver practices his trade at varying distances from the place where the yarn was manufactured, or if the yarn were stored for varying lengths of time before weaving. This results in obtaining fabrics with a different barr effect from the same kind of yarn and the barr is dependent on the time lapse mentioned.

This varying factor has been removed by the system according to the present invention. After rewinding the yarns on cros-swound bobbins the tendency for forming the above-mentioned b-arr effect no longer changes. with time to an unacceptably perceptible extent in the resulting fabrics. The duration of storing and transporting the crosswound bobbins is therefore no longer important, at least relative to the 'b arr effect mentioned.

The time elapsing between Winding on the draw-twisting pirn and rewinding onto crosswound bobbins, on the contrary, however, is of special importance. It has already been stated above that said period preferably should be less than 48 hours. The time available for said rewinding depends on the effectiveness with which the internal relaxation of the thread is accomplished. If the latter were less intensive, for example, then it is recommended that said rewinding be carried out within a shorter time than when a very intensive relaxation of the threads has been accomplished.

Very intensive relaxation gives particular advantages in the practical realization of this invention. In this case, delays in rewinding the twisting pirns onto crosswound bobbins-which delays are accompanied by longer storage of .the twisting pirnsdo not immediately result in yarns with an undesirably pronounced tendency for forming a barr effect. For this reason, a preferred embodiment of this invention is characterized by rewinding yarns which have been produced on a draw-twisting machine having a thread path of practically constant length between the stretching roller and the pirns, and wherein the relaxation treatment is carried out in said thread path as set forth in .said application Serial No. 708,689, now Patent No. 3,025,660, although the invention may also be practiced with other yarns, such as that produced by the process of said application Serial No. 823,718. By taking said measure during the draw-twisting of the yarns the fluctuations in tension occurring in the thread in said thread path when using the usual stretchtwisting machines are considerably reduced. Moreover, it has been found that the homogeneity of the internal relaxation is benefited thereby.

The constant variation in length of the thread path produced by the usual draw-twisting machines mentioned is caused by vertical movement of the traversing beam of said ring-twisting machines as a result of which the height of the thread balloon between the traveller and fixedly arranged top thread guiding eyelet formed during normal operation of the ring-twisting machines mentioned is caused by vertical movement of the traversing beam of said ring-twisting machines as a result of which the height of the thread balloon between the traveller and fixedly arranged top thread guiding eyelet formed during normal operation of the ring-twisting spindle continuously increases and decreases. The effect of this increase and decrease in length may be obviated in several ways. For example, a thread loop with varying length may be drawn between the last conveying roller arranged before the ringtwisting spindle and the top thread guide. In this way, the increase or decrease in length of said thread loop should fully compensate the decrease or increase in balloon height.

Another possibility exists in attaching the top thread guide to the traversing beam for movement therewith and by supplying thread to said thread guide at an angle of preferably with the center line of the twisting spindle. The thread path between said thread guide and the thread guide positioned immediately before said thread guide should be at least three times as long as the thread path between the top thread guide and the traveller. Tension fluctuations in the relaxation zone, that is the zone between the stretching roller and the traveller, will hardly occur in this case, as fully explained in said copending application Serial No. 708,689, now Patent No. 3,025,660.

Traversing of the top thread guide with the traversing beam is obtained in a simple way by fixing the guide on a support placed on the traversing beam. It is also possible, however, to couple the top thread guide and the traversing beam indirectly with respect to each other. The traversing of the top thread guide with the traversing beam to which the traveller ring is fixed results in constant balloon height between the traveller and the top thread guide during the entire twisting operation. As a result, the thread tension in the balloon also remains constant.

Instead of providing a thread supply at an angle of 90 with the center line of the twisting spindle, a different supply direction for the thread may also be chosen, for instance, at an acute angle with said center line. In that case, however, increases and decreases in length of the thread path occur between the stretching or drawing roller and the top thread guide unless a traversing auxiliary roller is applied. This roller pulls a thread loop with varying length in said thread path in such a way that variations in length counteract the fluctuations caused by the traversing top thread guide. In this embodiment the thread may be passed from the stretching roller upwardly to the traversing auxiliary thread guide and from there downwardly to the traversing top thread guide of the twisting spindle. In said deflection path, thread may be subjected to the relaxation treatment, for instance by being passed over a heated plate.

The invention will be further elucidated with reference to the accompanying drawing which shows in elevation an apparatus with which part of the method according to the invention may be carried out.

In the FIGURE, numeral 1 denotes a thread brake over which a thread 2 from a supply bobbin (not shown) is passed to a supply roller 3 driven by a motor (also not shown). In order to prevent the thread 2 from slipping over said roller 3 a pressure roller 4 is urged thereagainst and cooperates therewith in a'known manner. The surface of said pressure roller consists of an elastic material, such as cork. Said roller 4 is mounted in a swinging arm 5. The pressure roller 4 is driven only by the supply roller 3. This operation is produced by wrapping the thread :about the pressure roller 4 over an angle greater than with the aid of a thread guide 6. The thread guide is slowly traversed longitudinally of the pressure roller 4 in order to prevent an incision of the rollers.

After leaving the supply roller 3, thread 2 is passed over two snubbing pins 7 and subsequently is wrapped a number of times around a stretching or draw roller '8 which is rotated with a circumferential speed a few times greater than that of the supply roller 3. With the aid of an idler roller 9, the center line of which crosses the axis of the stretching roller 8 at a small angle, the thread wraps on the roller 8 are spaced from each other.

oneness Subsequently, the stretched thread is passed over a freely rotatable metal roller 16. Opposite part of the circumference of said roller 10, and in such a way that the thread can be passed to the same freely, there is arranged an electrical heating element 11 for heating the roller by radiation. From the roller the thread is passed to the top guiding eyelet which is formed as a roller with a circumferential groove 12. This roller 12 is freely rotatably supported by a supporting arm 13 mounted on a traversing beam 14. The traversing beam 14 is moved up and down in a known manner by a mechanism (not shown) and supports a ring 15 along which ring traveller 16 is movable. The ring is known per se and therefore not shown. A winding bobbin 18 is placed on the spindle.

Example In a practical embodiment of the method according to the invention an unstretched thread with 35 filaments, a titre of 35.6 tex. (approximately 320 denier), and consisting of polycaprolactam was first drawn between the rollers 3 and 8 of the abovedescribed apparatus to such an extent that the thread was lengthened 3.12 times. The thus stretched thread discharged from the stretching roller 8 at a speed of 360 m./rnin. and was thereupon heated on the roller 16 at a temperature of 113 C.

Subsequently, the thread 2 was passed through an air zone of 100 cm. up to the roller 32-, after which the thread was wound on the bobbin 18 while being twisted. The top thread guide 12 was arranged at a height of cm. above the traversing beam 14 so that the thread path in the balloon amounted to about cm. The weight of the traveller 16 was 38 mg, Whereas the ring 15 had a diameter of 8.7 cm. and the twisting spindle was rotated at 7900 revolutions per minute. As a result, the yarn was wound on the bobbin with a balloon tension of 0.4 g./tex. The shrinkage of the thread in the relaxation zone, that is, the zone between the stretching roller 8 and the bobbin 18, was about 2.3%

Yarns resulting from the aforesaid process had an elongation of 37% at a tenacity of 46 g./teX., were immediately rewound from the stretch-twisting pirns onto the crosswound bobbins, and were stored in this form until they could be woven. This was done after 12 weeks. The fabric obtained did not appear to show any barr effect.

If, however, the yarns are first stored on the drawtwisting pirns for more than one week, or in some instances for more than 48 hours, and then woven, the fabric obtained does show a barre effect although to a lesser degree than a fabric that had been produced from yarns which had not been relaxed after stretching.

For completeness sake, it is remarkable that with synthetic linear polycondensation products there are not only meant polyarnides which may be prepared from lactams, especially caprolactnrn or from diamines and dicarboxylic acids, especially those from adipic acid and heXamethylene diamine, but also polyesters, such as polymerized polymethylene terephthal-ates, especially polyethylene terephthalate.

Inasmuch as modifications falling within the scope of this disclosure will become apparent to those skilled in this art, it is intended that the present invention be limited only to the extent set forth in the following claims.

What is claimed is:

1. In a method for treating yarn formed from synthetic linear polycondensation products to eliminate pirn barre when woven into fabric wherein the yarn is drawn, relaxed internally, and twisted during collection on a pirn, the improvement comprising the step of rewinding said yarn from the pirn onto a crosswound package within 48 hours from the pirn collection and prior to substantial development therein of a tendency for forming barr.

2. A method for treating yarn formed from synthetic linear polycondensation products to eliminate pirn barr when woven into fabric, comprising the steps of successively drawing said yarn, internally relaxing said yarn while maintaining substantially constant the length thereof, twisting said yarn while collecting the same on a pirn, and rewinding the drawn and twisted yarn onto a crosswound package within 4-8 hours from the time of original collection.

References Cited in the file of this patent UNITED STATES PATENTS 2,491,569 Lichtenberg Dec. 20, 1949 2,800,762 Wurmli July 30, 1957 2,956,330 Pitzl Oct. 18, 1960 FOREIGN PATENTS 548,428 Belgium June 30, 1956 798,999 Great Britain July 30, 1958 800,555 Great Britain Aug. 27, 1958 

2. A METHOD FOR TREATING YARN FORMED FROM SYNTHETIC LINEAR POLYCONDENSATION PRODUCTS TO ELIMINATE PIRN BARRE'' WHEN WOVEN INTO FABRIC, COMPRISING THE STEPS OF SUCCESSIVELY DRWAING SAID YARN, INTERALLY RELAXING SAID YARN WHILE MAINTAINING SUBSTANTIALLY CONSTANT THE LENGTH THEREOF, TWISTING SAID YARN WHILE COLLECTING THE SAME ON A PIRN, AND REWINDING THE DRAWN AND TWISTED YARN ONTO A CROSSWOUND PACKAGE WITHIN 48 HOURS FROM THE TIME OF ORIGINAL COLLECTION. 